A method extends battery life of a battery powered indoor air quality (IAQ) sensor that includes a IAQ detector, a radio, the battery, and a microcontroller with a memory and a processor. The method includes detecting IAQ at predetermined intervals to provide IAQ levels, and storing the IAQ levels and corresponding timing data in the memory. The method further includes determining an occupancy schedule based on IAQ level patterns and subdividing the occupancy schedule into a plurality of periods. The method further includes determining an occupancy status of each of the periods based on the IAQ levels. The method further includes operating the IAQ detector to sample at an active interval when the occupancy status is the occupied and at an inactive interval when the occupancy status is the unoccupied. The inactive interval is longer than the active interval. The IAQ detector can be, for example, a CO2 detector or a VOC detector.